Mac – Centos running very slow in Virtualbox

I am running Centos 7 in Virtualbox 4.3.14. The VM is configured with

• 2 CPUs
• 4 GB RAM
• 3.10.0-123.4.4.el7.x86_64 kernel

The host machine is running

• Windows 7 Pro SP1 64-bit
• Intel i7-4790 CPU, Hyper-Threading enabled
• 16 GB RAM

Yet, when I start up this VM, it bring my entire system almost to a halt, including my host OS. In Process Explorer of System Internal, I can see all my cores are maxed out by VirtualBox. On my VM using top, the load average is about 2 when the system "idles".

• I have tried the dummy VM trick as per http://tech.shantanugoel.com/2009/07/07/virtualbox-high-cpu-usage-problem-solved.html
• I have tried the divider trick as per https://community.oracle.com/message/9307831
• I have tried disabling
  "Nested-Paging" as per … (cannot add more links with my rep)

Previously I used to run a similar configuration using only a laptop with 6 GB of RAM without any problems.

What else can I try to make this VM usable?